瞬态激励下冻融循环对桩-土耦合刚度影响试验

考虑桩-土的相互作用,在冻融循环作用下,土体的力学性质必然发生变化,构件的动力响应特性也会随之发生变化。为研究瞬态激励下冻融循环作用对桩-土耦合刚度的影响,设计和制作混凝土试验桩模拟基桩,通过压电陶瓷的正压电效应,利用压电智能骨料作为传感器测定冻融循环过程中瞬态激励下结构的波动响应,并对比分析两种不同土体含水率下压电信号的特性和能量大小,提供一种基于压电智能骨料的结构动力响应实时监测方法。试验结果表明,在冷冻过程中,瞬态激励下各测点时域波形幅值减小,而融化过程中,各点的时域波形幅值增大,且土体含水率越高,时域波形幅值变化越大;多次冻融循环后,瞬态激励下的桩-土耦合刚度变小。在不同含水率时,离瞬态激励点最近的两块压电陶瓷(piezoelectric ceramics, PZT)的能量指数平均差别分别为30%、25%,在含水率为6%时,平均每一次冻融循环会使桩-土耦合刚度减小约6%,而在含水率为12%时,平均每一次冻融循环会使桩-土耦合刚度减小约10%。12%的含水率相比6%的含水率,其对桩-土耦合刚度的影响大约高68%。

An experimental study of Freeze-thaw cycle influencing on the coupling stiffness of pile and soil under transient excitations

With the consideration of a pile-soil interaction, the mechanical properties of soil must change under the effect of freeze-thaw cycle, dynamic response characteristics of the component will also change accordingly. In order to investigate freeze-thaw cycle influencing on the coupling stiffness of pile and soil under transient excitations, the concrete test pile have been designed and manufactured. Through the direct piezoelectric effect of piezoelectric ceramic, piezoelectric ceramic smart aggregate (SA) is used as a sensor to measure wave response of the structure under transient excitation in the process of freeze-thaw cycle, then contrastive analysis the characteristics and energy of piezoelectric signal under two different moisture content, lastly providing a real-time monitoring method of structural dynamic response based on piezoelectric ceramic smart aggregate. The experimental results show that the amplitude of the time domain waveform decreases in the freezing process and increases in the thawing process. The soil moisture content is higher, the greater the amplitude of the time domain waveform changes. The coupling stiffness of pile and soil under transient excitations decreases after repeated freezing and thawing cycle.When the water content is 6%, the coupling stiffness of pile-soil decreases by about 6%, while when the water content is 12%, the coupling stiffness of pile-soil decreases by 10%. The influence of 12% moisture content on pile-soil coupling stiffness is about 68% higher than that of 6%.